Question

A car of mass 1000kg is stopped by applying
brakes over a distance
, if the initial velocity
of the car 54 km/hr calculate the retarding
force applied by brake​

Answer 1

Answer:

The force is -3000 Newtons so, the retarding force is 3000 Newtons.

Explanation:

$m = 1000 kg$

$u = 54 km/h = 54 × \frac{5}{18} = 15 m/s$

$v = 0m/s$

(There is no time given in the question so assume it as 5 seconds because vehicles mostly take just 5 seconds for such retardation and it is universally accepted to take 5 seconds in such situations)

First Equation of Motion :

$v=u+at$

$0=15+(a×5)$

$a=\frac{0-15}{5}$

$a=-3m/{s}^2$

From Newton's Second Law of Motion we know that :

$F=ma$

$F=1000×-3$

$F=-3000N$

NOTE : To solve this problem we have assumed that the car is travelling in a straight line and it is uniformly accrlerated because equations of motion don't work if the motion isn't 1D or is non uniformly accelerated but unfortunately this is the best we can do at this stage. And also we have assumed 5 seconds as time but the real time may be different so our answer may be a approximate answer but again this is the best we can do.